Display consoles controlled by a graphic processor comprise a random access graphic memory interposed between the screen of the console and the processor which stores the data relative to each point or "pixel" of the graphic diagram appearing on the screen. The modification of the graphic diagram may be obtained any time by changing the contents of the data relative to each point of the diagram memorized in the graphic memory, which results in modifying the luminance and/or the color of each point or pixel of the graphic diagram which is to be modified. The modification is usually carried out by an operator who, using a keyboard connected to the processor, feeds in the instructions for modifying the data relative to each of the modified points. The action of the operator on the keyboard initiates in the processor a modification cycle which is executed either by initiating a particular program or by bringing into action wired logic operators.
Although the programming methods used allow a very high and complex number of replacement operations to be effected at low cost, they have as disadvantage the fact of occupying much of the computing cycle time of the processor. On the other hand, use of wired logics provides a saving in processing time but has the disadvantage of being expensive and to be limited to the use of elementary logic operators which very substantially reduces the possibilities of wired logic systems.